Ann Leckie’s first novel is an ambitious undertaking. Ancillary Justice is set in a space-opera universe, but with very little of the action taking place in space. Instead, the travels and travails of its narrator are mostly planet- or habitat-bound, and its exotica are more social and psychological than, say, cosmological or even military. In this very-far-future, humankind has spread across a considerable swathe of the galaxy, producing a wide variety of cultures and human types. But for the last few thousand years the ruthlessly expansionist interstellar regime of the Radchaai has been bringing reluctant systems into its hegemony via the euphemistically-named process of ‘‘annexation,’’ which has a more than passing resemblance to the rough-handed conquer-absorb-’’civilize’’-and-self-enrich pattern of the Roman Empire. But Radchaai encounters with powerful alien species – particularly with the Presger, who are more potent and even more arrogant and ruthless than themselves – precipitate a crisis at the core of the Radchaai polity, and the wavefront of that crisis collapses the world of the narrator, who calls herself Breq, in almost every way imaginable. (We will return to the narrator’s nature, identity, and gender shortly.)

The novel is also fairly ambitious structurally: a present-action plot thread starts on the backwater world of Nilt and moves toward vengeance, or at least an accounting, for Breq; and in alternating chapters, a back-story thread covers the events that led to the reasons for said accounting. As in Iain M. Banks’s Use of Weapons, some of the puzzling aspects of the present action are eventually explained in the antecedent-action thread, which also serves to outline the nature, culture, and standard practices of the Radchaai military-political empire. And a thousand years before those events lie other formative incidents, including the scouring of an entire solar system as punishment for a serious bit of resistance to annexation. After the back- and front-story threads meet, the book shifts modes to become (among other things) what might be called an intrigue of manners, as Breq copes with the complexities of Radchaai culture and the schemes of its absolute ruler.

Now about the cast: The person calling herself Breq has some trouble thinking of herself as an individual, since she is the sole surviving element of a company of ‘‘ancillaries’’ – brain-wiped human bodies run by an artificial intelligence that also operates a military starship, Justice of Toren. She is now reduced to one body (with, to be sure, some significant upgrades) and a tiny fragment of the Justice of Toren’s larger mind:

I had once had twenty bodies, twenty pairs of eyes, and hundreds of others that I could access if I needed or desired it. Now I could only see in one direction, could only see the vast expanse behind me if I turned my head and blinded myself to what was in front of me.

Ancillaries – ‘‘corpse soldiers’’ to unsympathetic non-Radchaai – are the preferred troops for implementing an annexation: there can be no breaches of loyalty or discipline, since the governing AI always obeys the ship’s human officers; when the order comes down to shoot a bunch of resistant annexees, they get shot, with no question or hesitation. Nor is there is any looting or rape or (unapproved) massacre, as there might be with human troops. Radchaai officers are in turn quite loyal to their central authority, Anaander Mianaai, Lord of the Radch – who is herself a many-bodied being operated by a single intelligence.

When the story opens, Breq has been a singleton for nineteen years and has come to the wintry world of Nilt in pursuit of an object that will allow her to have a mortal showdown with the Lord of the Radch. But along the way she saves the life of Seivarden, a drug-addicted former Radchaai officer who has also lost her social context and connection after surviving a thousand years of suspended animation in a ship’s escape pod. Seivarden’s rehabilitation becomes, willy-nilly, part of Breq’s mission, and the displaced officer – a quite conventional Radchaai – serves as a foil to Breq’s multiply-estranged sensibility as they travel across Nilt and then on to a regional palace, where Breq intends to confront the avatar of Anaander Mianaai in residence.

Now to that matter of gender: One of the features of Radchaai culture is a resolute refusal to use gender-marked pronouns – and it’s not only a grammatical but a social and (presumably) ideological matter. After two decades among non-Radchaai, Breq experiences a bit of culture shock on returning to the norms of her home space.

I saw them… through non-Radchaai eyes, an eddying crowd of unnervingly ambiguously ungendered people…. Short hair or long, worn unbound…. Thick-bodied or thin-, faces delicate-featured or coarse-, with cosmetics or none…. All of this matched randomly with bodies that one moment moved in ways various non-Radchaai would call feminine, the next moment masculine. Twenty years of habit overtook me, and for a moment I despaired of choosing the right pronouns, the right terms of address.

I know how she feels – I still can’t figure the biological sex of some of the characters, and Breq rarely provides cues – so I am following their, and Breq’s, native-language/culture conventions here and using feminine forms for all the Radchaai characters.

Another side of the novel’s ambition is the way it is deeply engaged with the tropes and issues of the science fiction of the last forty years or so. As I read, I made a mental list of writers I was reminded of: Susan Matthews (for the rigid, expansionist interstellar regime and the variegated human subtypes), Ursula K. Le Guin (gender-identity ambiguities and the frozen landscape of the opening chapters), C.J. Cherryh (estranged and/or estranging characters and exotic social frameworks), plus hints of Iain M. Banks and Neal Asher (AI-run starships and habitats, cyborgish characters, tough-minded use of violence). Which is not to reduce what Leckie has built here, but to offer some map coordinates that might help locate the work in its genre space.

And that genre space is quite engaging: a revenge-quest intertwined with a set of figure-my-culture puzzles wrapped around a reluctant-buddies adventure-travelogue, climaxing in a series of revelations and action-movie physical confrontations. The complexity and strangeness of the world that generates all this requires a degree of patience at the beginning – there is a large dose of guess-my-world in the book’s DNA, and some of the questions one puzzles over are necessarily left unanswered for some time. But patience is rewarded. This is not entry-level SF, and its payoff is correspondingly greater because of that.